When I worked for job A in IN, I only contributed $100 in traditional IRA, and contributed the rest of $5900 when I worked for job B in IL. Right now, I am not seeing a $100 deduction in my IN income, instead, I am seeing close to a $1000 deduction (TurboTax somehow automatically allocated $1000 IRA deduction towards IN and $5000 towards IL). Due to other deductions in IN return, my final number for IN return remains the same for both a $100 or $1000 deduction. However, for my IL return, I can get an extra $50 if I can "allocate" the entire $5900 deduction for IL income. According to another post, https://ttlc.intuit.com/community/retirement/discussion/ira-deduction-multiple-states/00/390059 , it makes more sense to allocate my IRA deductions to the state based on where I was a resident of when the IRA contribution was made.
